Esters



Patented Sept. 5, 1944 UNITED STATES PATENT o rica 2.351.594 ss'rsas 7Donald J. Loder, Wilmington, and Wilber o.

Teeters, Roselle,-Dei., assignors to E. L du Pont de Nemours & Company,Wilmington, DeL, a

corporation of Delaware No Drawing. Application June I Serial No.340,474

' Claims. (01.260-484) I The present invention relates to new materialsand to methods for their preparation, and more particularly, to thepolyhydric alcohol esters of alkoxy and alkoxy methylene substitutedacetic acids; and methods for their preparation. The

esterifying substituted glycolic acid with glycols and glycerol,respectively. A i urther object of the invention is to provide monoanddi-substituted glycolic acid esters of ethylene glycol and polyethyleneglycols and the mono-, diand tri-glycerides of substituted glycolicacids, together with processes for their preparation. Other objects andadvantages of the invention will herein-after appear.

These objects as well as others which will be apparent as thedescription proceeds, may be accomplished by reacting a lower alkylester of an oxy-substituted acetic acid with a polyhydric alcohol underconditions favorable to the interchange of alcohol radicals. Thisinterchange ol alcohol radicals is eflected by heating the alcohol andester together, preferably in the presence of alkaline alcoholysiscatalysts. The ester interchange proceeds more readily if the alcoholselected for reaction with the ester boils at a higher temperature thanthe alcohol liberated by the interchange, because the latter alcohol isthen more readily removed from the zone of reaction, for example, bydistillation.

The ester interchange process described above may be employed for thepreparation of either the monoglycolates or the polyglycolates, forexample, when it is desired to prepare ethylene glycol monoglycolate, inaccord with the ester interchange process, equimolecular proportions ofthe ester and ethylene glycol are reacted. If,

on the other hand, the reaction mixture contains two moles of the ester.per mole of the ethylene glycol and the reaction continues tocompletion, the product will be ethylene glycol diglycolate. In likemanner, it it is desired to obtain 9. glycerol monoand di -glycolate orglyceryl tri-glycolate, one mole of glycerol is reacted with one, two,or three moles of an ester of glycolic acid. The process is applicablegenerally to the preparation 0! polyhydric alcohol, monoandpoly-glycoiates, monoand poly-alk'oxy glycolates and monoand poly-olkoxymethoxy from thepolyhydric alcohols and the lower alkyl esters of,respectively, glycolic acid. CHziOHlCOOH, alkoxy acetic acids, CH2(OR)COOH', such as methoxy acetic acid, CH2(OCH:)COOH, and alkoxy methoxyacetic acids, CH:(OCH2OR) COOH, such as methoxy methoxy acetic acid,

CHz(OCH2OCHa)COOH The methyl, ethyl, propyl, isopropyl, butyl, isobutyl,amyl, etc. esters of this acid, may be reacted with the poiyhydricalcohols generally, such, for example, as: the glycols, e. g., ethyleneglycol, propylene glycol, butylene glycol, amylene glycol, diethyleneglycol, trimethylene glycol,

octadecanediol, tetramethylene glycol, hexamethylene glycol, or thealcohols. containing more than two hydroxyl groups, subh as glycerol,

diglycerol, triglycerol, trimethylol methane and 'trimethylol propane;sugars, such as, dextrose, sucrose, xylose, galactose, fructose,maltose, and

mannose;' and the sugar alcohols, such as, sor

.bitol, mannltol, and dulcitol; as well as castor oil (glyceryltriricinoleate), hydrogenated castor oil (hydroxy stearin), and likelong chain polyhydric alcohols.

This invention likewise includes esters otglycolic acid, alkoxyandalkoxy methoxy-acetic acids with ether alcohols, i. e., polyhydricalcohols having at least one free hydroxyl group, one or more hydroxylgroups being etherified. Examples of such ether alcohols include themonoalkyl ethers of ethylene glycol, such as the monomethyl, -ethyl,-propyl or -butyl ethers of ethylene'glycol, propylene glycol, etc.Esters of this class would be, e. g., ethylene glycol monomethyl etherglycolate, ethylene glycol monoethyl ether glycolate, ethylene glycolmonomethyl ether methoxy acetate, CHa(OCI-Ia)COOCHaCHa0CI-Ia.

and ethylene glycol monomethyl ether methoxy methoxy acetate,

CH=(OCH: OCH3) COOCHzCI-IzOCHa The monoand di-glycolates oi themonoglycerides are likewise included, e. g., the monoglycolates of themonoglyc'erides,

OH: (OH) COOCH2CHOH.CH2OOCR in which R is methyl, ethyl, propyi, butyl,etc. The monoglycerides of stearic acid, oleic acid, palmitic acid,etc., may be used for the preparation of these monoand di-glycolates.

Polyhydric alcohol esters as well as ether alcohol esters oi substitutedglycolic acids may likewise be prepared by the aforesaid esterinterchange process. For example, such esters of the following acids arealso included in the present invention: the alkoxy acetic acids,

on= omcoon e. g., ethoxy-, propoxy-,- isobutox'y-acetic acids, w E etc.;the alkoxy alkoxy acetic acids,-

e. g., ethoxy methoXy-, propoxy methoxy-, isobutoxy methoxy-aceticacids, etc.; and the alkoxy carbomethoxy methoxy acetic acids,CH2(OCH2OCH2COOR) COOH, e. g., -methoxy carbomethoxy methoxy acetic acidor ethoxy oarbomethoxy methoxy acetic acid, which may,

be prepared by reacting glycolic acid .formals with carbon monoxide inaccord with the process described in the copending application of S. N.256,854, filed Februaryl'l, 1939.

The esters of the present invention are preferably prepared by the abovedescribed ester interchange process, for the reason that this processprovides a means of obtaining both the monoand poly-glycolates inexcellent purity and yield. Simple esteriflcation may be employed,however, that is, by the interaction of the polyhydric alcohol with theglycolic acid. There appears to be one exception to this, in that, dueto the dehydrating characteristics of glycolic acid, it does not reactreadilywith glycerol but forms acrolein at the expense of the glycerolester and,

consequently, simple esteriflcatlon should preferably not be employedwhen the glycerol esters' of glycolic acid are desired.

The invention likewise provides another ester interchange process forthe preparation 01' esters of g'lycolic acid. This process involves theinteraction of a polyhydric alcohol or ether alcohol with glycolide,which may be considered to be a poly-ester of glycolic acid. Thisreaction may be effected by first forming the glycolide (prepared,

e. g.. in the usual manner by 'heating the glycolic' acid to drive offall the water), and subsequently reacting the glycolide (which may bepresent as a diglycolide, or as a polyglycolide) with the polyhydricalcohol. If a partially dehydrated glycolic acid is used, e. g., adiglycolide or polyglycolide in the presence of free glycolic acid, theinitial reaction is carried out under reflux and 'then water of esterification, of free glycolic acid EXAMPLE I-Ermrtanr: GLYcor.MONOGLYCOLATE (A) To 2250 parts (25 moles) of methyl glycolate was added1550 parts (25 moles) of ethylene glycol and, as catalyst, a solution of3.0 grams of sodium in 7 grams of methanol (30% sodium methoxidesolution). This mixture was refluxed under a fractionating column,fitted with a distilling head arranged for controlled reflux, until thehead temperature had receded to 64-65 C. The methanol was removed asrapidly as possible at the head of the column, the

head temperature being carefully maintained be tween 64 C. and 66 C. Therefluxing and the collecting'of the methanol were continued forapproximately ten hours, at the end or which time approximately 800grams (25 -moles) of methanol had been collected.

The heat was discontinued and any low boiling material which remainedwas removed by vacuum distillation. (If desired the color of the productmay be improved'by treatment with 2 per cent of its weight of a standarddecolorizing charcoal. For most purposes, however, the color of theuntreated ester was satisfactory).

(B) To 310 parts (5 moles) of ethylene gly col, contained in a suitable3-necked flask equipped with an efficient stirrer and reflux condenser,was added 290 parts (5 moles) of powdered polyglycolide, prepared bycompletely dehydrating glycolic acid at elevated temperatures (mo-220C.) The temperature of the reaction mixture was raised to and held at atemperature of -200 C., preferably between -200 C., for a period ofapproximately five hours.

In both- (A) and (B) the reaction mixture was cooled, and the productobtained was a pale amber-colored liquid which contained 98 to 99 percent. of glycol monoglycolate. The yield was substantially quantitative,based on either the glycolor glycolate; sp. gr. was 1,283 60 F./60 F.and the saponiflcation number was 460.

' ExAMrLr: IIE'rHYLEN1: DIeLYooLA'rE The conditions and procedure arethe same as Product Yield quantitative. uid. Sp. gr. 1.32'7/20/4. Sap.No. 611.

EXAMPLE III-GLYCEROL MONOGLYCOLATE The conditions and procedure are thesame as Example I.

Quantities Parts Moles Methyl glycolate 1, 980 22 Glycerol (96%) 2. 10822 Anhydrous potassium carbonate (catalyst) 10 Methanol ofl 704 ProductYield quantitative. Pale amber colored liquid. Sp. gr. 1.320 60/60 F.Sap. N0. 380.

' Exam Ln IV-GLYCER L DIGLYCOLATE The conditions and procedure are thesame as for Example I.

Products from (A) and (B) are identical in constants.

Products from (A) and (B) are identical in constants.

Amber colored viscous liq- Amber colored viscous liquid. 20/4.

, Sodium methoxide (321%(555550'111331::::::

Yield substantially quantitative in both cases. SP. 81'. 1.393 Sap. 542.

Exnnmn' v- -Brre-nmoxr Erma. GLYcoLArr.

Up to and through the removal of methanol the conditions are the same asExample I.

Quantities Parts Moles Methyl glycolate 990 11 Beta-ethoxy ethanol(Cellosolve)- 900 l Catalyst:

1 part Na in 4 parts of methanol...

Anhydrous otassium carbonate. 5

Methanol o 309 9.7

The refluxing and the collecting of the methanol were continued until nomore methanol was liberated. The reaction mixture was cooled and thecalculated quantity oi -concentrated sulfuric acid added to form theneutral sulfate salt. The neutralized product was vacuum distilled andthe beta-ethoxy ethyl glycolatedistilled,- giving' 75 to 90% yield. Itwas found to be a mobile, colorless liquid having the followingconstants: B. P. l62.-163 C./120 mm. Sap. No. theoretical 378; found375. Y

ExAM PLE VI-Bnn-msmoxy ETHYL GLYCOLATE To amixture oi 769 parts moles)of crystalline glycolic acid and 760 parts (10 moles) of beta-methoxyethanol was added 2 parts of concentrated sulfuric acid and 50 parts ofbenzene {water carrier). The reaction mixture was heated to refluxtemperature and the water of esterification, which separated as a lowerlayer in a suitable decanting type distilling head, was removed. Whenthe distillate no longer formed two layers theheat was discontinued andthe crude ester cooled. The acid catalyst present in the crude mixturewas exactly neutralized with anhydrous potassium carbonate and thebetamethoxy ethyl glycolate distilled and recovered in a yield of 70to80%. It was recovered as a mobile, colorless liquid having a B. P. of155- l56/135 mm; a sp. gr. of 1.163 60/60 F. and a saponification numberof 417.

ExAiuPLn VIIOcrAnncANEnro1, DIGLYCOLATE quantitative yield of the ester.

- Quantities Parts Moles on? "llnl 429 1.6 Isobutyl glycolata. 396 8. 0

Product Q White low melting solid. Sap. No. theoretical 194; found 184.

EXAMPLE VIII-CAsron On. Gzrcowrn glycolata'lllxample'vn.

Quantities Parts Moles 5 Castor-oil 888 l Isobutyl glycolate. 396 3Sodium methoxide (catalyst) 3.0 parts 01' 30% in methanol Product 10Yield substantially quantitative. Amber reddish' viscous liquid. Sap.No, 242.

EXAMPLE- 1XETHYLENE GtYcor. Monomnrnox Acnnrr:

Procedure the same as Example I (glycol monoglycolate) with theexception that, after the reaction mixture was cooled, the alkalinecatalyst was exactly neutralized with sulfuric acid and the productdistilled under reduced pressure.

. Quantities Parts Moles Methyl methoxy acetate 260 2. 5 Ethylene glycol155 2. 5 Sodium methoxide (catalyst) in mcthanol) 2 Product Yieldsubstantially quantitative. Colorless liquid. B. P. 141-142 C./25 mm.Sp. gr. 1.174 60/ 60 F. Sap. N0. 420,

EXAMPLE X-ETHYLENE BIS-METHOXY ACETATE Procedure same as for Example IX.

liquid. B. P. 176-177 C./25 mm. Sp. gr. 1.194 60/60 F. Sap. N0. 555.

EXAMPLE m 369 parts of methyl (methoxy methoxy) 'acetate, 744. parts ofethylene glycol, 10 parts of litharge, and 5 parts of zinc oxide wererefluxed at 150 mm., the methanol of reaction being removed as rapidlyas formed. When the evolution or methanol ceased, the catalyst wasdestroyed by precipitation with carbon dioxide and the resultingsolution filtered toremove the Precipitated catalyst. The excess ofethylene glycol was removed by distillation'at 1 mm. pressure and glycolmono (methoxy methoxy) acetate,

CHaOCHzQCHzCOOCHsCHzOH a colorless mobile liquid, miscible with waterand with methanol was obtained in an 82% yield. This compound has adensity at 25 C. '01 1.1776 and a refractive index of N" 1.44.02.

Exiurru: XII

670 parts oi! methyl (methoxy methoxy) ace tate, 80.6 parts 0! ethylene.glycol, 14 parts of litharge, and 7 parts of zinc oxidewere refluxed atmm., the methanol of reaction being removed as rapidly as formed. Whenmethanol Procedure the same aslor octadecanediol diceased to be evolved,th'ecatalyst was precipi- CHzO OHIO CHIC O O CHzCHzO O C CHgO CH,

was obtained in good yield. It is a high boiling, water white liquidwhich is soluble in water and methanol and is a solvent for cellulosenitrate. It has a density at 25 C, of 1.2021 and a refractive index of N1.4375.

In place of the sodium .methoxide of the examples, other alcoholysiscatalysts may be used such as sodium ethoxide, sodium glyceroxide, andalkali metal alkoxides generally; sodium hydroxide, anhydrous potassiumcarbonate, calcium oxide, litharge, etc.; or mixture of the two types.Alkaline alconolysis catalysts are, in general, more satisfactory,though in some instances, acid alcoholysis catalysts, e, g., sulfuric,p. toluene sulphonic acid, and hydrochloric acids, may be employed. Thepolyhydric alcohol esters and ether-esters of glycolic acid, as well asthe other esters described herein, have many characteristics whichparticularly fit them for uses in the arts. They are all generallyuseful as solvents or plasticizers for many natural and synthetic resinswhich are used with or without pigments,

fillers, extenders and the like, which compositions are employed for thepreparation of lacquers, pigments, paste pigments, etc., or for theformation of films, filaments, rods, tubes, or shaped articles. Morespecifically, they are generally useful a solvents, plasticizers andsofteners for natural resins, such, for example, as damar, copal, kuriand forthe synthetic resins, such, for example, as the alkyds;cumarone-indene; chlorinated diphenyl; soluble types of polymerizedhydrocarbons, phenol-formaldehyde and urea-formaldehyde resins; estergum; polymeric acrylic and methac'rylic acids and their esters, amides,nitrlles, imides, salts, interpolymers, and other derivatives; polyvinylalcohol; the polyvinyl esters; styrene and other polymeric resins, aswell as simple mixtures of the natural and/ or synthetic resins, and/orinterpolymers of the polymeric resins. The polyhydroxy alcohol esters ofglycolic acid are also useful as solvents, plasticizers or softeners ofregenerated cellulose and the cellulose derivatives, such as, celluloseacetate, nitrate, acetonitrate, aceto-propionate, methyl cellulose,ethyl cellulose and other organic derivatives of cellulose or mixturesthereof.

The polyhydric alcohol esters of glycolic acid are likewise generallyapplicable as the major ingredients in the preparation of printing padsand ink feeders of all types, as penetrating agents for printing pastes,and'as major ingredients in the preparation of inks, both for theprinting of paper, textiles, wood, metal or other materials.

The ethylene glycol monoglycolate, diglycolate and glycerol mono-,di-and tri-glycolate, may be used as softeners for glassine paper, as asubsticute for glycerine in tobacco, as a softener for regeneratedcellulose and as a substitute for glycerol .in printing inkcompositions. They have likewise been found acceptable for the sizing ofthe arti- :ncial and natural silks and particularly for the sizing ofregenerated cellulose filaments and fabrics and are also most effectiveas softening agents for cotton, .wool, linen, :Iute, rayon and silk.

Glycolate esters of the alkyl ethers of polyhydric alcohols such, forexample, as glycolic glycol, HOCHzCOOCHzCI-IzOR, are, as has beengenerally stated above, excellent solvents for cellulose ethers andcellulose esters. These compopolyhydric alcohol esters of glycolic acid,are excellent solvents and liquid media for certain dyestufis andpigments wherein they may be substituted for the ethers of thepolyhydric alcohols.

The polyhydric alcohol sters and ether-esters of 'glycolicacids,hereinbeforedescribed, may also be used as ingredients in thepreparation of compounds for defrosting and anti-misting; in cosmeticpreparations; as dye-solvents for basic acid and direct dyes; as thefluid medium for electrolytic condensers; as ingredients in leatherfinishes and varnish removers; as solvents and fixatives for perfumes;as .softeners for cork binders, glue, gelatin, paper and textile sizes;as an ingredient in dentifrice compositions; as softeners for casein,zein, soybean, protein plastics, etc.; as an ingredient in leak-proofingcompositions for gas distributing systems, gas masks and the like; inthe preparation of wetting, dispersing and penetrating agents, etc.,such as sulfates and acid esters of the monoalkyl ethers of ethylene, u

the like; as precipitation inhib'itors; and as ingredients in fluids forhydraulically actuated mechanisms.

The phosphate derivatives of the polyhydric alcohol glycolates arelikewise useful as plasticizers generally for use in combination withthe aforementioned natural and synthetic resins, as well as thecellulose ethers, esters, and regenerated forms of cellulose.

The esters of the alkoxy acetic acids, in addition to the uses abovedescribed. for the glycolic esters of the alkyl ethers of the polyhydricalcohols and because of their large number of active solvent groups, areparticularly excellent s01- vents for'gases, liquids, solids and resins.The excellent solvent properties of materials of this type canbeattributed to the combination of ether and ester groupings.

1. A process which comprises alcoholysis of an ester of a substitutedacetic acid having the structural formula, ROCHzOCHzCOOI-I, in which Ris an alkyl group with a polyhydric alcohol ether.

2. A process which comprises alcoholysis of an ester of a substitutedacetic acid having the empirical formula, ROCHaOCHiCOOE' in which R isan alkyl group with a mono alkyl ether of ethylene glycol.

3. A process which comprises the alcoholysis of an alkyl hydroxy acetatewith a polyhydric. alcohol ether.

, 2,307,094 4 A prggess which comprises the alcoholysis of an'ester ofmethoxy acetic acid with a mono alkyl ether of ethylene glycol.

9. A process which comprises the alcoholysis of an ester of (methoxymethoxy) acetic acid with a mono alkyl ether-oi ethylene glycol.

10. A process tor the preparation of a polyhydric alcohol ether ester01' hydroxyacetic acid which comprises heating in contact with analcoholysis catalyst a hydroxyacetic acid ester or a lower aliphaticalcohol with a polyhydric alcohol ether containing a free hydroxylgroup.

11. A process for the preparation 01' a (monoalkyl ether of ethyleneglycol) ester 01' hydroxyacetic acid which comprises heating methylhydroxyacetate with a monoalkyl ether 01' ethylene glycol in contactwith an alcoholysis catalyst.

12. A process for the preparation of p-ethoxy ethyl glycolate whichcomprises refluxing methyl glycolate, p-ethoxy ethanol, methanol, andanhydrous potassiumcarbonate and subsequently recovering by distillationthe p-ethoxy ethyl glycolate.

13. A process for the preparation of p-methoxy ethyl glycolate whichcomprises heating under reflux glycolic acid, p-methoxy ethanol,sulfuric acid, and benzene and subsequently separating from the reactionproduct p-methoxy ethyl glycolate. I

14'. A glycol monoalkyl ether ester of methoxy methoxy acetic acid.

15. Glycol monomethyl ether ester of (methoxy methoxy) acetic acid,

CHaOCHzOCHCOOCHaCHzOCI-Ia DONALD J. LODER. 'WILBER O. TEE'I'ERS.

